This patent document relates to optical communication systems, including techniques for communicating information using wavelength division multiplexing (WDM) techniques.
The single-channel optical transmission rate has been significantly increased in the recent years, as evidenced by the introduction of new technologies and products. In this regard, 100 Gigabit (Gb) Ethernet powered by dual polarization quadrature phase shift keying (DP-QPSK) with digital coherent demodulation will become commercially available soon. However, the industry has reached a point that the speed of electronics, the bandwidth of opto-electronic interfaces, as well as the required optical signal-to-noise ratio (OSNR) at higher modulation levels, all impose significant challenges to further increases in single-channel bit rates to meet the expected network capacity demand at 1 Tb/s and beyond.